Evaluation of Respiratory Exposure Dose of Uranium Mine Dust Particulate Matter Filtered by Mask

Compared with ordinary mines, there are still a large number of long-life 234U, 238U, 226Ra, 230Th, 210Po and other long-lived uranium dusts in uranium mines.αradionuclide. These long-lived uranium dust particlesαRadionuclides contribute greatly to the internal exposure dose caused by human respiration, which will cause great harm to the health of practitioners. At present, many scholars have evaluated the risk of uranium dust breathing exposure. Panigrahi et al. [1] conducted radioactive aerosol monitoring on the Jaduguda uranium mine in India. The monitoring results showed that the geometric mean concentration of radionuclides was 16.84 mBq/m3, with a standard deviation of It is 3.21; Jha et al. [2] analyzed the monitoring data and found that there is a linear correlation between the total concentration of uranium dust and the concentration of nuclides, and the correlation coefficient is 0.43; Tomasek et al. Mine dust was monitored, and the results showed that the median diameter AMAD of radioactive aerosol activity ranged from 2.0 to 9.2μm (average is 7.3μm), the corresponding geometric standard deviations are 2.1-6.5 (average is 3.2). Long life of 234U, 238U, 226Ra, 230Th, 210Po in uranium dustαRadionuclides are fine particles. Masks have a certain filtering effect on fine particles. In previous studies, most of the previous studies ignored the filtering effect of masks on uranium dust, or for safety reasons, an empirical coefficient of 0.3 to 0.5 was taken. If the influence of wearing a mask on the calculation of human body radiation dose caused by uranium dust is ignored, this will inevitably lead to a high calculation result [4], and the selection of the safety factor lacks basis, and its accuracy and scientificity need to be proved. Therefore, this paper uses two commonly used gauze masks and KN95 masks in uranium mines. On the basis of mastering the real data of uranium dust mass concentration and particle size distribution after filtering by these two masks, the effect of uranium dust particles on breathing is calculated. Exposure to human body exposure and respiratory exposure risk index from uranium dust. The doses and risk values ​​calculated in this paper do not include the contribution of radon and its progeny. 1 Respiratory exposure risk assessment model Health risk assessment is based on the damage of pollutants to the human body, combined with toxicology-related data, to establish an assessment model of the degree of damage to human health caused by different types of pollutants. The International Agency for Research on Cancer divides pollutants into genetic substances (including radioactive substances and other carcinogens) and somatic toxic substances (non-carcinogenic substances) [5-6], which can be divided into respiratory, dietary and skin routes according to different exposure routes. contact route. As the main step of occupational exposure risk assessment, respiratory exposure risk assessment is an important tool for assessing the current or potential exposure of humans to hazardous substances, and is also an integral part of epidemiological research. The respiratory exposure risk index is used to describe the degree of interaction between the human body and the pollutants when the human body is exposed to harmful substances through the respiratory route, and is an important parameter to evaluate the risk degree of human exposure to external substances. 7]: In the formula, R is the lifetime risk of equivalent death due to a specific harmful health effect; AAD (Average Annual Doses) is the average annual exposure dose of chemical pollutants, mSv/a; RFD is the pollutant in The reference dose under a certain exposure route, mSv/a. Among them, the pollutants involved in uranium miners are radioactive substances; the occupational exposure dose control value RFD in the uranium mining and metallurgy industry is 15 mSv/a[8]. The main occupational exposure to uranium dust is respiratory exposure, and the average annual exposure dose AAD can be calculated by the formula [9-10] as follows: where IR is the respiratory volume, m3/d; EF is the exposure frequency, d/a; ED is the equivalent exposure duration, a; F is the filtration efficiency of the mask, dimensionless; fi is the dose conversion factor of the ith nuclide, Sv/Bq; Ci is the activity concentration of the ith nuclide, Bq/m3. The internal exposure hazard caused by uranium dust to the human body mainly comes from its long life.αHowever, since the measured uranium dust concentration is a mass concentration, in order to calculate its radiation dose to the human respiratory tract, it needs to be converted into an activity concentration. Therefore, the conversion is carried out according to the following formula: Strictly speaking, the mass fraction of uranium in uranium ore dust is not the same as the grade of uranium ore, but the actual measurement found that the mass fraction of uranium in uranium mine dust is not higher than the average grade of ore, In formulas (3) and (4), it is reasonable and safe to replace the mass fraction of uranium in uranium dust with uranium grade.